A schoolboy trying to save his youth club was hauled from class after his plan to protest outside David Cameron's constituency office was spotted - by anti-terror police.
In an astonishing over-reaction, 12-year-old Nicky Wishart was warned he faced ARREST.
"I couldn't believe it," he said. "The policeman asked me lots of questions about why we were having a protest and who would be there.
"I said it was simply because we didn't want our youth centre to close - it's a fantastic place to go and there isn't much else for us to do round here."
The full-scale security operation swung into effect days after Nicky made an innocent request on Facebook to "save our youth centre".
The surprised boy was told police were now monitoring his Facebook posts - which are mainly gossip and banter from school about lessons and friends' haircuts.
He was told he would be responsible for any "trouble" at the well-mannered picket on Friday night.
Public-spirited Nicky, one of the PM's constituents in the Oxfordshire seat of Witney, said: "All this is because Mr Cameron is our local MP and it's a bit embarrassing for him."
He said the police arrived during an English lesson on Tuesday afternoon.
"I was taken out of class - and the policeman said, 'Are you aware that the anti-terrorist squad are looking at your Facebook account?' He said that if anything got out of hand, they would arrest people.
"Then he said that I could get arrested for organising it. I was frightened and wished my mum was with me."
Nicky, who describes himself as a "maths geek, not a rebel or rioter", said: "Then the policeman asked, 'Does your mum know about this?' I said, 'Yes, of course, she supports it.'
"But the policeman carried on, 'Are you sure your mum wants you out protesting at night?' He was trying to scare me off - but there was no way I wasn't going to go."
In opposition, Mr Cameron often spoke of the need to keep youth clubs open to give youngsters a constructive way to spend their time.
He said in 2007: "Before people break the law, we need strong families, we need youth clubs, we need things to divert people from crime."
But, as part of the Con-Dem cuts, Tory-run Oxfordshire County Council is axing £4million of funding for 20 clubs - including the one in Nicky's home village, Eynsham.
The council claims volunteers might take over as part of Mr Cameron's "Big Society".
But Nicky says that if funding for the five staff at the centre is removed, it will be forced to close in March.
The well-used centre, catering for children aged 10 to 18 has a music room, pool table, table-tennis and coffee bar.
Nicky set up a Facebook group called Save All UK Youth Centres, which now has 649 members.
At Friday's hour-long demo, he, his sister Beth, 14, and a dozen friends waved home-made placards outside the PM's office in Witney accompanied by two youth workers.
The picket was watched by four police officers on the other side of the street. Two more officers were nearby.
Liz Brighouse, leader of the council's Labour group, said: "For anti-terror police to get involved is complete madness.
"This is a community-spirited 12-year-old we are talking about."
Nicky's mother Virginia, 41, said: "The school phoned on Monday to say the anti-terror police had been looking at his Facebook.
"I said it was OK for police to speak to him, but assumed I'd be there and I was appalled they interviewed him without me.
"Nicky has done nothing wrong. He's been brought up to be respectful and I support what he's doing."
Thames Valley police said an officer interviewed Nicky, with his head of year sitting in.
A spokesman said: "This was not to dissuade his protest but to obtain information to ensure his and others' safety."